A wireless communication system may include a number of base stations (e.g., cellular base stations, WiFi access points, or the like) that radiate to define wireless coverage areas, such as cells and cell sectors, in which user equipment devices (UEs) such as cell phones, tablet computers, tracking devices, embedded wireless modules, and other wirelessly equipped communication devices (whether or not controlled by a human user), can operate. In turn, each base station may be coupled with network infrastructure, including one or more gateways, routers, and switches, that provides connectivity with one or more transport networks, such as the public switched telephone network (PSTN) and/or a packet-switched network such as the Internet for instance. With this arrangement, a UE within coverage of a base station may engage in air interface communication with the base station and may thereby communicate via the base station with various remote network entities or with other UEs.
In a typical system, each base station's coverage area may operate on one or more carrier frequencies and may define various channels for carrying control and bearer communications between the base station and the UEs in the base station's coverage area. Further, the base station may work with UEs in its coverage to manage assignment and/or use of various air interface resources, such as particular channels or portions of channels, for carrying communications to and from the UEs. For instance, as the base station receives packet data from the network infrastructure for transmission to UEs on various bearers, the base station may queue the data, schedule use of particular downlink air interface resources (e.g., channels, resource blocks, or the like) to carry the data, and transmit the data on the scheduled resources to the destination UEs. Likewise, as UEs have data to transmit on various bearers, the base station may schedule use of particular uplink air interface resources to carry the data, and the UEs may transmit the data on the scheduled uplink resources to the base station.
Optimally, a wireless service provider will strategically implement base stations throughout a market area so that served UEs can move between the base station coverage areas without loss of coverage. Each base station may include an antenna structure and associated equipment, and the wireless service provider may connect the base station by a landline cable (e.g., a T1 line) with the service provider's network infrastructure to enable the base station to communicate with a signaling controller (e.g., MME), gateway system, other base stations, and the like.
In practice, however, it may be impractical for a wireless service provider to run landline connections to base stations in certain locations. For instance, where a service provider seeks to provide many small coverage areas blanketing a market area or to fill in coverage holes between coverage of other base stations, the service provider may implement many small-cell base stations throughout the market area, but it may be inefficient or undesirable to run landline cables to every one of those small-cell base stations.
To connect a base station with the network infrastructure in such a situation, the wireless service provider may implement a wireless backhaul connection between the base station and another base station of the service provider's network. In this situation, the base station at issue operates as a relay base station, and the other base station operates as a donor base station. In practice, the relay base station includes or is coupled (e.g., via a local area network or other connection) with a UE, referred to as a relay-UE, and the donor base station then serves the relay-UE in much the same way that the donor base station serves other UEs. Further, the relay base station itself serves UEs, in much the same way that any base station would. For example, when a UE enters into coverage of the relay base station, the UE may signal to the relay base station to initiate an attach process, the UE may acquire an IP address, and an MME may engage in signaling to establish one or more bearers between the UE and a gateway system. Each of these bearers though, would pass via the wireless backhaul connection.
Further, in such wireless communication systems, a media server communicate streaming media content to UEs, and therefore, base stations sometimes transmit streaming media content to their served UEs. Such streaming media content may include audio and/or video. While a UE is receiving streaming media content, variations in network conditions can adversely affect the user experience. For example, if the available bandwidth suddenly decreases, a user of the UE may notice a degradation in quality, such as a media stream that stalls or buffers.
Adaptive bit rate streaming is one technique to reduce such problems. Adaptive bit rate streaming works by adjusting in real time the bit rate of the streaming media content based on knowledge of a UE's wireless conditions. The bit rate refers to the number of bits that are conveyed or streamed per unit of time (e.g., number of bits per second).
In one implementation, an encoder encodes a particular instance of media content at multiple bit rates, yielding multiple versions of the instance of media content each having a different bit rate. For instance the encoder may establish different versions having different bit rates by changing the frame rate and/or resolution at which each version is encoded.
Further, to stream the instance of media content to the UE, the media server then selects an appropriate version of the instance of media content, and communications the selected version to the UE. As the media server streams the instance of media content to the UE, the media server may switch between streaming different versions to the UE depending on the UE's wireless conditions. For example, initially, the media server may stream a version of the instance of media content with a first bit rate. As the UE receives streaming media content from the media server, the UE or the UE's serving base station may send a message to the media server regarding the UE's RF conditions. And if, for instance, the UE's RF conditions decrease, the media server may switch to streaming a version of the instance of media content that is encoded at a lower bit rate than the first bit rate. Adjusting the bit rate over time may reduce buffering time and allow faster starting times. Further, the ability to adjust the bit rate for different UEs may enable the media server to provide good user experiences for both UEs with good wireless conditions and UEs with poorer wireless conditions.